In this project, a taxonomy of motor dysfunction will be developed for children ages 1 to 42 months who have movement disorders. Included are: * Cluster analysis of performance of Motorically Challenged children (n = 250) to determine if specific subgroups can be uncovered; * Concurrent and discriminative validity studies (n = 125 Normals and 250 Challenged) on a new procedure for analyzing Quality of Movement and on the Bayley Motor Scale to determine if groups can be differentiated; * Development of a system to ascertain if children fit into one of the empirically derived groupings of motor dysfunction; and * Expanding the knowledge base in Motor Dysfunction, developing a theoretical model which accounts for variance within the group of Motorically Challenged young children. Previous approaches to the diagnostic assessment of motor functioning typically have focused on tabulating units of motor skill, or motor milestones, and not on assessment of qualitative aspects of movement, such as transitions between positions and maintenance of stable functional positions. The techniques which emerge from this research will assist in designing treatment programs for children with motor delays and dysfunction. They will also be beneficial in diagnostic assessments of children with motor challenges, and in treatment efficacy research.